This is an ongoing a thread about my adventures in modding my 2-year old Gaggia Evolution, and I'll be logging my progress as I go along I'm done. While the mods I'm attempting aren't new, they've never been described in detail for an Evolution AFAIK, so this may be useful for owners of the less expensive Gaggia machines. The plan is to install a PID, an OPV and preheat tubing with in-line pressure gauge to my Evolution. Chime in if you have solutions to my problems!

First thing I did was to go through the parts in the rather expensive PID kit. It looks well put together. Included in the package are a CD-ROM instruction disc, various cables, thermal grease, adhesive pads, a screw-on PRT sensor, a SSR, and a PID controller with case. The SSR is a Carlo Gavazzi RS1A40D25, rated to switch up to 25A at 400VAC. Unfortunately, the CD included in my kit was unreadable in my computer.

Looking at the SSR, I realized I'd run into showstopper #1. There is no heatsink included in the kit and the Evolution has an all-plastic exterior, so sinking the SSR to the casing is a no-go. First I'll need to find myself a proper heatsink.

Aug 11, 2009.Opening up the Evolution was rather tricky as it was not designed to be opened up easily. Here I'll explain how to open up the Evolution without damaging the fragile plastic case.Before you begin: allow the boiler to cool to room temperature for at least a couple hours after use. You can get some nasty burns from residual hot water inside the boiler!To protect yourself from electric shock, disconnect the power cable from the wall socket and the machine. Do not work on a powered machine!

Opening the machine:

Using a flat-head screwdriver, unlatch the four plastic tabs that hold the front panel down. (Figure 1)

With the same screwdriver, lift the small plastic cap in the top panel. (Figure 2)

Place the machine in an upright position. Unscrew the top panel screw with a philips head screwdriver. (Figure 3)

With the machine still upright, remove the four hex socket screws around the group with a 5/32 allen key. (Figure 4)

Carefully lift the top panel with one hand while pushing the steam valve handle into the machine with the other. The top panel should come off easily with no force. (Figure 5)

The inside of the machine should now be accessible. Make a record of all the connections before you do anything else! (Figure 6)

Now with the machine open, I decided to completely disassemble the group head to clean out the insides. Make a note of all the electrical and water connections before proceeding further! I wrote numbers on the electrical connectors with a sharpie pen and took pictures of the boiler and pump.

Disassembling the boiler and group head:

Disconnect the electrical connectors from the boiler and pump. There are eight connectors on the boiler and four on the pump.

Unscrew the four philips-head screws that secure the mounting plate to the case. (Figure 6)

Lift out the mounting plate and place on work surface. Using a wrench, remove the thermostats from the boiler. (Figure 7)

Unscrew the two hex socket screws at the boiler inlet with a 5/32 allen key. Disconnect the boiler from the rest of the mounting plate and be prepared for water spilling from the boiler inlet. (Figure 8)

Unscrew the four hex socket screws holding the boiler halves together with a 5mm allen key. Again, be prepared for spilling water as the boiler halves are separated. (Figure 9)

With the boiler base plate removed, unscrew the two hex socket screws that secure the steam valve assembly with a 5mm allen key. These screws will be screwed on very tightly. Be very careful not to break the heater element pins while fighting with the screws! I cracked one of the ceramic insulating posts but fortunately did not destroy the element. (Figure 11)

Returning to the boiler base plate, unscrew the group head valve with a wrench. (Figure 12)

Clean off lime scale from the boiler parts as best as you can. Scrub away!

After cleaning the boiler group, I decided to push ahead with the steam valve mod and OPV installation.

The Evolution steam valve assembly has a self-priming valve feature (bug?) that vents excess boiler pressure via a plastic tube into the water reservoir. Unfortunately, this valve can fail and vent during shot extraction, reducing the pressure available to the puck. I decided to replace the Evolution steam valve assembly with one without the self-priming feature.The Evolution OPV is installed on the pump outlet, and vents through the mounting plate into the reservoir below. It appears to be adjustable with a flat-head screwdriver through the vent hole from below, once the reservoir is moved out of the way. I chose to replace the Evolution boiler inlet with the OPV from the Gaggia Classic. The idea is to set the boiler inlet OPV to 8-9 bar, and leave the pump outlet OPV at 11 bar as a secondary safety measure.

Steam valve and OPV mod:

Screw on the two hex socket screws with a 5mm allen key to secure the non-self-priming valve assembly to the boiler. (Figure 13)

Re-seat the boiler o-ring on the boiler base before assembling the boiler halves with a 5mm allen key and four hex socket screws. (Figure 14)

Using a wrench, screw on the group head valve to the boiler base. (Figure 15)

Secure the Classic boiler inlet OPV to the boiler using a 5/32 allen key and two hex socket screws, then re-attach inlet hose from pump and re-assemble onto mounting plate. (Figure 16)

Lower the mounting plate into the case, making sure it is seated well. You may have to jiggle the counter-weighting rod in the back of the case to get the mounting plate to seat correctly. (Figure 17)

Reconnect all thermostats and electrical connectors. Remember not to secure the boiler group to the mounting plate until after you replace the top panel. (Figure 18)

I performed a quick adjustment of the new OPV using the "backflow" method. I improvised a blind filter using some Saran wrap placed over the portafilter, as described here. Placing the OPV return tube in a measuring cup, I measured the return flow as I turned on the pump. I was afraid that I would melt the plastic wrap and so I disconnected the boiler heating elements during this test. Fortuitously, the as-installed OPV required no tuning, as it returned about 125 ml in 30 s in three separate trials. This should place the pressure at around 8-9 bar, although I will verify this once I install the pressure gauges.

Aug 12, 2009After re-assembly, I decided to monitor the air temperature inside the Evolution. This is important because it impacts the choice of heat sink for the SSR, if the SSR assembly is to be placed within the case. To make this measurement, I used the PID controller as a thermometer by wiring up the PRT sensor without connecting an SSR (view). Boiler temperature is still controlled by the stock Evolution thermostats at this time. After replacing the top panel and priming the pump, I allowed the machine to warm up for half an hour. The highest air temperature attained was about 108 F (43 C), with the boiler on steam mode.

Aug 18, 2009Received in mail today:

Carlo Gavazzi heatsink kit (RHS100, Ebay, $14)

I used the air temperature measurements to select this particular heatsink, and I'll detail some of the calculations involved. The Evolution's 1425W boiler is rated for 13 A at 110 V. If the Gavazzi SSR is used to source this current to the boiler, it must dissipate just about 12 W in heat through the SSR casing. Assuming that the temperature within the case goes up to 50 C, I need a heat sink with a thermal resistance of less than 4 K/W, so that the SSR core does not heat beyond the safety limit of 125 C (SSR datasheet). The RHS100 heat sink I've purchased has a documented thermal resistance of 3.5 K/W under these conditions (heatsink datasheet). I've over-engineered by assuming a higher internal case temperature, and by selecting a heat sink with a thermal resistance well under the safety threshold.

Having received the heatsink, I decided to go ahead with the full PID mod.

PID installation:

Prepare PID assembly for installation, following instructions included in PID kit. (Figure 18)

Prepare PRT sensor by dabbing a small amount of thermal conductive grease on the screw tip. (Figure 19)

Use double-sided tape to affix SSR assembly to the inside of machine case. Take care to apply it only to the SSR plastic case and not on the heat sink, as the heat sink gets hot during operation. (Figure 21)

Attach the SSR to the inside wall as shown here. There is just enough space to fit the assembly between the case and the pump inlet. (Figure 22)

Upon receiving the pressure gauge, I scrounged around and found some 1/4" OD copper and teflon tubing as well as several Swagelok joints. Time to perform the preheat tubing mod.

Installing preheat tubing with pressure gauge:

Wrap a layer of teflon thread sealant tape around the gauge NPT threads before attaching Swagelok adapter. NPT threads will leak under pressure if sealant tape is not used. The Swagelok joint used is a 1/8" NPT female to 1/4" OD tube fitting adaptor. (Figure 24)

Use two wrenches to tighten the Swagelok joint securely on the gauge. (Figure 25)

Disassemble the boiler group from the machine and tightly wind 5 feet of 1/4" OD copper tubing around the boiler by hand. Remove the boiler inlet OPV and the steam valve tubing for easier access. (Figure 26)

Use a Swagelok union joint with 1/4" OD tube fitting and some 1/4" OD teflon tubing to connect one end of the copper windings to the boiler inlet OPV. (Figure 27)

Use a Swagelok 1/4" OD tube fitting tee to join the other end of the copper windings to a 8-10" length of straight copper tubing. Bend the straight tubing so that it runs parallel and under the steam valve tubing. The final tee input will be attached to the pump outlet. (Figure 28)

Replace the boiler group in the machine. There is just enough space to run the steam valve tube and the copper tube through the casing hole. Attach the pressure gauge to the straight copper tubing. (Figure 29)

Bend the pressure gauge tubing so that the pressure gauge can be read comfortably. (Figure 30)

Next I measured the 30 s backflow volume of the Invensys CP3A pump at various OPV settings, using an improvised blind filter. The pressure was read off the gauge and oscillated rapidly within a ~2 bar range due to vibrations from the pump. The results are:

150 ml @ 7.5-9.0 bar (average 8.25 bar)

130 ml @ 8.4-10.2 bar (average 9.3 bar)

120 ml @ 9.0-11.0 bar (average 10.0 bar)

110 ml @ 9.6-11.6 bar (average 10.6 bar)

These points can be fitted rather well by a line with equation: Volume in ml = -16.9 * Pressure in bars + 290This may be useful for other Evolution owners who wish to use the backflow method to ballpark the brew pressure between 8-10 bars.

Finally, here's an action shot from the first brew attempt with all mods installed!

Sorry to be dragging up an old thread but I felt it apt given my predicament.

I'm trying the mod to my Evolution with the same Auber PID and am approaching the power connection rather cautiously. I have everything else wired up ok but I'm a little confused with the power.

Starting with the mains power connector [Kettle lead]. There are 4 plugs as opposed to 2. 2 which are piggy backed. I assume that these are the grounding connectors but that leads me to ask where I should connect the PID to neutral power. See here: Click Here (lh6.ggpht.com)

The other issue regards the Main power switch on the front of the machine. One of these traces back to the Mains power connecter [Kettle lead] whilst the other connects to the other switches and also back to the boiler. I'd of thought that the former is the one to connect up but given the other piggy backing i'm rather confused.

Yeah the mod worked out. I eventually figured out what was the correct configuration. We've been using it for months now. There are some questions about a lack of acidity in shots and wonder if it is related to the true pressure value. I've also had someone post on my blog about how true the pressure is on a device that lacks a 3 way solenoid.

Sorry to bump this thread, but I had a question about the four 5/32 allen screws that hold the group in place. When I go to loosen them, they break free and then get a LOT harder to loosen as they turn out, nearly siezing at about 3/4 turn. Is there some kind of thread sealant on these that makes them so hard to turn out?

Next I measured the 30 s backflow volume of the Invensys CP3A pump at various OPV settings, using an improvised blind filter. The pressure was read off the gauge and oscillated rapidly within a ~2 bar range due to vibrations from the pump. The results are:

I had a play with my Gaggia Classic today turning the OPV 180 degrees counter clockwise. The espresso is much better, thicker and creamier. I haven't got a pressure gauge so tried the return flow thingy (using a blind basket) for 30 seconds and I think I'm in the ball park of 120ml. What I would like to know is: does the 30s start when you press the brew button or when you first see water coming from the tube (which is around 8 seconds after the brew switch is turned on)?

If your machine has a 3-way solenoid (Classic) you count from when the button is hit.

If your machine does not have a 3-way solenoid (Evolution, Coffee or Carezza for example) then the water must build enough pressure to overcome the resistance of a spring and ball valve located just above the shower screen screw. With these machines you count from the first water flow for accurate measurement.

I chew coffee beans with my teeth while gargling with 195 F water to enjoy coffee. What is this "coffee brewing" device you speak of?

Hi all,first of all apologize my writing.I bought a week ago an evolution,and read about a simple mod that drops the brew presure around 9-9.5 bar,but I'm not 100% sure what to screw/unscrew,how many degrees,(maybe because it's new and i'm afraid to do more damage:) )only that is related to opv valve placed on top of the boiler or the one placed outside the vibrating pump,based on the pictures that I attached can someone help me,also if there are other mod that don't involve any costs I would be grateful if someone could help me,thanks

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